Explicit realization of affine vertex algebras and their - PowerPoint PPT Presentation

Notre Dame 2015 Explicit realization of affine vertex algebras and their applications Draˇ zen Adamovi´ c University of Zagreb, Croatia Supported by CSF, grant. no. 2634 Conference on Lie algebras, vertex operator algebras and related topics A conference in honor of J. Lepowsky and R. Wilson University of Notre Dame August 14 - 18, 2015 Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Affine vertex algebras Let V k ( g ) be universal affine vertex algebra of level k associated to the affine Lie algebra ˆ g . V k ( g ) is generated generated by the fields x ( z ) = � n ∈ Z x ( n ) z − n − 1 , x ∈ g . As a ˆ g –module, V k ( g ) can be realized as a generalized Verma module. For every k ∈ C , the irreducible ˆ g –module L k ( g ) carries the structure of a simple vertex algebra. Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Affine Lie algebra A (1) 1 Let now g = sl 2 ( C ) with generators e , f , h and relations [ h , e ] = 2 e , [ h , f ] = − 2 f , [ e , f ] = h . g is of type A (1) The corresponding affine Lie algebra ˆ 1 . The level k = − 2 is called critical level . For x ∈ sl 2 identify x with x ( − 1) 1 . Let Θ be the automorphism of V k ( sl 2 ) such that Θ( e ) = f , Θ( f ) = e , Θ( h ) = − h . Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Affine Lie algebra A (1) in principal graduation 1 Let � sl 2 [Θ] be the affine Lie algebra � sl 2 in principal graduation [Lepowsky-Wilson]. � sl 2 [Θ] has basis: { K , h ( m ) , x + ( n ) , x − ( p ) | m , p ∈ 1 2 + Z , n ∈ Z } with commutation relations: [ h ( m ) , h ( n )] = 2 m δ m + n , 0 K [ h ( m ) , x + ( r )] = 2 x − ( m + r ) [ h ( m ) , x − ( n )] = 2 x + ( m + n ) [ x + ( r ) , x + ( s )] = 2 r δ r + s , 0 K [ x + ( r ) , x − ( m )] = − 2 h ( m + r ) [ x − ( m ) , x − ( n )] = − 2 m δ m + n , 0 K in the center K Proposition. (FLM) The category of Θ –twisted V k ( sl 2 ) –modules coincides with the category of restricted modules for � sl 2 [Θ] of level k. Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 N = 2 superconformal algebra N = 2 superconformal algebra (SCA) is the infinite-dimensional Lie superalgebra with basis L ( n ) , H ( n ) , G ± ( r ) , C , n ∈ Z , r ∈ 1 2 + Z and (anti)commutation relations given by 12 ( m 3 − m ) δ m + n , 0 , [ L ( m ) , L ( n )] = ( m − n ) L ( m + n ) + C [ L ( m ) , G ± ( r )] = ( 1 2 m − r ) G ± ( m + r ) , [ H ( m ) , H ( n )] = C 3 m δ m + n , 0 , [ H ( m ) , G ± ( r )] = ±G ± ( m + r ) , [ L ( m ) , H ( n )] = − n H ( n + m ) , 3 ( r 2 − 1 {G + ( r ) , G − ( s ) } = 2 L ( r + s ) + ( r − s ) H ( r + s ) + C 4 ) δ r + s , 0 , [ L ( m ) , C ] = [ H ( n ) , C ] = [ G ± ( r ) , C ] = 0 , {G + ( r ) , G + ( s ) } = {G − ( r ) , G − ( s ) } = 0 for all m , n ∈ Z , r , s ∈ 1 2 + Z . Let V N =2 be the universal N = 2 superconformal vertex algebra. c Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 N = 2 superconformal algebra N = 2 superconformal algebra (SCA) admits the mirror map automorphism (terminology of K. Barron): κ : G ± ( r ) �→ G ∓ ( r ) , H ( m ) �→ −H ( m ) , L ( m ) �→ L ( m ) , C �→ C which can be lifted to an automorphism of V N =2 . c Proposition. (K. Barron, ..) The category of κ –twisted V N =2 –modules coincides with the category of c restricted modules for the mirror twisted N = 2 superconformal algebra of central charge c. Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Correspondence When k � = − 2, the representation theory of the affine Lie algebra A (1) is related with the representation theory of the N = 2 1 superconformal algebra. The correspondence is given by Kazama-Suzuki mappings. We shall extend this correspondence to representations at the critical level by introducing a new infinite-dimensional Lie superalgebra A . Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Vertex superalgebras F and F − 1 The Clifford vertex superalgebra F is generated by fields Ψ ± ( z ) = � n ∈ Z Ψ ± ( n + 1 2 ) z − n − 1 , whose components satisfy the (anti)commutation relations for the infinite dimensional Clifford algebra CL : { Ψ ± ( r ) , Ψ ∓ ( s ) } = δ r + s , 0 ; { Ψ ± ( r ) , Ψ ± ( s ) } = 0 ( r , s ∈ 1 2 + Z ) . Let F − 1 = M (1) ⊗ C [ L ] be the lattice vertex superalgebra associated to the lattice L = Z β, � β, β � = − 1 . Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Vertex superalgebras F and F − 1 Let Θ F be automorphism of order two of F lifted from the automorphism Ψ ± ( r ) �→ Ψ ∓ ( r ) of the Clifford algebra. F has two inequivalent irreducible Θ F –twisted modules F T i . Let Θ F − 1 be the automorphism of F − 1 –lifted from the automorphism β �→ − β of the lattice L . F − 1 has two inequivalent irreducible Θ F − 1 –twisted modules F T i − 1 realized on (1) = C [ β ( − 1 2 ) , β ( − 3 M Z + 1 2 ) , . . . ] . 2 Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 N = 2 superconformal vertex algebra Let g = sl 2 . Consider the vertex superalgebra V k ( g ) ⊗ F . Define τ + = e ( − 1) ⊗ Ψ + ( − 1 τ − = f ( − 1) ⊗ Ψ − ( − 1 2 ) , 2 ) . Then the vertex subalgebra of V k ( g ) ⊗ F generated by τ + and τ − carries the structure of a highest weight module for of the N = 2 SCA: � k +2 Y ( τ ± , z ) = � 2 n ∈ Z G ± ( n + 1 2 ) z − n − 2 G ± ( z ) = Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Kazama-Suzuki and ”anti” Kazama-Suzuki mappings Introduced by Fegin, Semikhatov and Tipunin (1997) Assume that M is a (weak ) V k ( g )-module. Then M ⊗ F is a (weak) V N =2 –module with c = 3 k / ( k + 2). c Assume that N is a weak V N =2 –module. Then N ⊗ F − 1 is a (weak ) c V k ( sl 2 )–module. This enables a classification of irreducible modules for simple vertex superalgebras associated to N=2 SCA (D.Adamovi´ c, IMRN (1998) ) Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Kazama-Suzuki and ”anti” Kazama-Suzuki mappings: twisted version Let c = 3 k / ( k + 2). Assume that M tw is a Θ–twisted V k ( g )-module. Then M tw ⊗ F T i is a κ –twisted V N =2 –module. c Assume that N tw is a κ –twisted V N =2 –module. Then N tw ⊗ F T i − 1 is c a Θ–twisted V k ( g )–module. Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Lie superalgebra A A is infinite-dimensional Lie superalgebra with generators S ( n ) , T ( n ) , G ± ( r ) , C , n ∈ Z , r ∈ 1 2 + Z , which satisfy the following relations S ( n ) , T ( n ) , C are in the center of A , 3 ( r 2 − 1 { G + ( r ) , G − ( s ) } = 2 S ( r + s ) + ( r − s ) T ( r + s ) + C 4 ) δ r + s , 0 , { G + ( r ) , G + ( s ) } = { G − ( r ) , G − ( s ) } = 0 for all n ∈ Z , r , s ∈ 1 2 + Z . Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 The (universal) vertex algebra V V is strongly generated by the fields � 2 ) z − n − 2 , G ± ( z ) = Y ( τ ± , z ) = G ± ( n + 1 n ∈ Z � S ( n ) z − n − 2 , S ( z ) = Y ( ν, z ) = n ∈ Z � T ( n ) z − n − 1 . T ( z ) = Y ( j , z ) = n ∈ Z The components of these fields satisfy the (anti)commutation relations for the Lie superalgebra A . Let Θ V be the automorphism of V lifted from the automorphism of order two of A such that G ± ( r ) �→ G ∓ ( r ) , T ( r ) �→ − T ( r ) , S ( r ) �→ S ( r ) , C �→ C . Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Lie superalgebra A tw A tw has the basis n ∈ Z , r ∈ 1 S ( n ) , T ( n + 1 / 2) , G ( r ) , C , 2 Z and anti-commutation relations: 1 2 + Z {G ( r ) , G ( s ) } = ( − 1) 2 r +1 (2 δ Z r + s ( r 2 − 1 r + s ( r − s ) T r + s + C 3 δ Z r + s S ( r + s ) − δ 4 ) δ r + s , 0 ) , S ( n ) , T ( n + 1 / 2) , C in the center , with δ S m = 1 if m ∈ S , δ S m = 0 otherwise. Proposition. The category of Θ V –twisted V –modules coincides with the category of restricted modules for the Lie superalgebra A tw . Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications

Notre Dame 2015 Theorem (A, CMP 2007) Assume that U is an irreducible V –module such that U admits the following Z –gradation � V i . U j ⊂ U i + j . U j , U = j ∈ Z Let F − 1 be the vertex superalgebra associated to lattice Z √− 1 . Then � � U i ⊗ F − s + i U ⊗ F − 1 = L s ( U ) , where L s ( U ) := − 1 s ∈ Z i ∈ Z and for every s ∈ Z L s ( U ) is an irreducible A (1) 1 –module at the critical level. Draˇ zen Adamovi´ c Explicit realization of affine vertex algebras and their applications